Recently, electronic devices that incorporate touch panels therein have been spreading widely. Touch panels are mounted in many devices including small screen, such as portable phones, PDAs (Personal Digital Assistants), or the like. In the future, it can be envisaged sufficiently that such touch panels will be incorporated into equipment having large sized screens that serve as PC (Personal Computer) displays or the like.
In the case of conventional touch panel electrodes, indium tin oxide (ITO: Indium Tin Oxide) primarily is used in view of the translucent properties thereof. It is known that the electric resistance per unit area of ITO is comparatively high compared to other metals or the like. More specifically, in the case of ITO, as the (total area of the touch panel) screen size increases, the surface resistivity in the electrode as a whole tends to increase. As a result, a problem arises in that the transmission speed of current between the electrodes becomes slower, such that the time (i.e., response speed) required to detect the contact position after the touch panel has been touched is delayed.
Therefore, various techniques have been proposed in which surface resistivity is decreased by constituting the electrodes in a plurality in the form of a lattice by means of thin wires (thin metal wires) made up from metal having low electrical resistance (see, for example, International Publication No. 1995/27334, International Publication No. 1997/18508, and Japanese Laid-Open Patent Publication No. 2003-099185).
For example, if the same mesh patterns are regularly arranged in a uniform manner, there is a disadvantage that, in relation to pixels constituting the display screen, moiré phenomena (interference patterns) are generated easily. Therefore, various techniques have been proposed for suppressing noise granularity (referred to generally as graininess), which occur in conjunction with moiré phenomena, by arranging the mesh pattern regularly or irregularly, thereby improving visibility of an observation target or object to be observed.
For example, as shown in FIG. 57A, according to Japanese Laid-Open Patent Publication No. 2009-137455, a window for a riding movable body and the shape of a pattern PT1 thereof in plan view are disclosed, having a mesh layer 4, in which rounded arcuate conductive wires 2 from which portions have been cutout are arranged repeatedly in a lattice shape, and respective ends of the arcuate wires 2 are connected in the vicinity of a center portion of another adjacent arcuate wire 2. In accordance therewith, it is noted that not only visibility but also shielding of electromagnetic waves as well as resistance to breakage can be improved.
Further, as shown in FIG. 57B, according to Japanese Laid-Open Patent Publication No. 2009-016700, a transparent conductive substrate and the shape of a pattern PT2 thereof as viewed in plan are disclosed, which is manufactured using a solution, i.e., a self-organized metal particle solution, which forms a mesh-like structure naturally on the substrate if one side of the substrate is coated and then left untreated. In accordance therewith, it is noted that an irregular mesh-like structure can be obtained in which moiré phenomena do not occur.
Moreover, as shown in FIG. 57C, according to Japanese Laid-Open Patent Publication No. 2009-302439, a light transmissive electromagnetic shield material and the shape of a pattern PT3 thereof as viewed in plan are disclosed, in which an electromagnetic shield layer 6 has a sea region structure in a sea-island configuration, wherein the shapes of island regions 8 made up from openings surrounded by the electromagnetic shield layer 6 differ mutually from each other. In accordance therewith, it is noted that both optical transparency and electromagnetic shielding are improved without the occurrence of moiré phenomena.